Recently, in video reproduction technology, high-definition content such as 4K content has been developed. Along with the development of high-definition content, content management systems for managing content keys and content encrypted with the content keys in combination are required to have higher encryption strength by using longer content keys and the like as well as higher access security by adopting more complex content key access methods.
In particular, according to conventional encryption key generation methods, even if there are several protected regions in a memory for storing a content key, the content key is simply stored in a specific single protected region. Further, when a host device reads the content key, the content key is exchanged in an encrypted state, but the content key is simply encrypted with a content encryption key which is cut out from a specific fixed portion of a common bus key obtained beforehand in authentication processing between the host device and the memory (such as an SD card). Therefore, the access security needs to be further improved.